import java.util.Scanner;

public class d073_分組報告 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String input, output;
		int mate_no;
		int team_no;
		
		while(sc.hasNext()) {
			input = sc.nextLine();
			mate_no = Integer.parseInt(input);
			
			team_no = 0;
			
			team_no = mate_no / 3;
			
			while(mate_no % 3 != 0 && mate_no != 0) {
				team_no++;
				break;
			}
			
			output = Integer.toString(team_no);
			
			System.out.println(output);
		}
	}
	
}